This invention relates to micromechanical switching devices formed by semiconductor batch fabrication techniques. More specifically, this invention relates to switches of the aforementioned type wherein the device is formed to have a cantilever beam extending over a shallow recess for deflection into and out of engagement with a fixed member at a side of the recess opposite that at which the cantilever beam is supported.
Switches of the aforementioned type are known (see for example articles by Kurt E. Petersen: "Micromechanical Membrane Switches on Silicon", July, 1979, IBM J. Res. Develop., Vol. 23, No. 4, pp. 376-385 and "Silicon as a Mechanical Material", May, 1982, Proceedings of the IEEE, Vol. 70, No. 5, pp. 420-457.) Such switches may be of the single-contact low-current type wherein the cantilever beam serves as a current carrying movable contact member engageable with a fixed contact or may be of a double-contact configuration for carrying higher currents. In the latter instance a bridging contact bar is fixed to the cantilever beam to project in opposite directions normal to the major dimension of the cantilever beam for bridging a pair of fixed contacts. The aforereferenced articles describe in detail the various steps of layer growth and formation, metallization, photoresist applications and etching to arrive at the desired structure through semiconductor fabrication techniques. In the aforementioned switches, the recess over which the cantilever beam is suspended has a p.sup.+ silicon at the bottom surface of the recess. A voltage applied between the p.sup.+ layer and the metallization at the upper surface of the cantilever beam establishes a capacitive effect which applies an electrostatic force on the cantilever beam, pulling it downward until the unsupported end of the cantilever beam makes contact with a fixed stop or electrical contact. While these switches are suitable for their intended purposes, the electrostatic forces utilized therein do not provide adequate contact forces to permit the use of such switches for typical mechanical switching applications.